e_racer1999 Posted July 30, 2004 Share Posted July 30, 2004 i want med/high compression, and i'm gonna be running flattop/slight dome pistons... i have both heads, and if i use the e88 i am going to use the valves from the N47... so which is better for a street application? -jason Quote Link to comment Share on other sites More sharing options...
ecp48 Posted July 30, 2004 Share Posted July 30, 2004 Jason, There is a program called the Nissan L6 Engine calculator. It was put together by the guys at the Sydney Z Car Club. The link below should take you to it. It has been posted on this site several time as well. The program is downloadable. It allows you to input your parameters such as your head choice and gives you what you are looking for., even data on your proposed destroke 2.8. If you can't find it email me and I will send it to you. e88 : 9.80:1 n47 : 9.82:1 ecp48 http://HTTP://infovfj.ozemail.com.au/zcar.html Quote Link to comment Share on other sites More sharing options...
e_racer1999 Posted July 30, 2004 Author Share Posted July 30, 2004 thanks for the info.. i was just wondering from the viewpoint of someone who has done one (or both?) of the combinations who could give me some insight. i know that each has its pros and cons, such as the ccs i nthe combustion chambers, the size/shape of the exhaust ports, etc... but thanks for the tip! -jason Quote Link to comment Share on other sites More sharing options...
ecp48 Posted July 31, 2004 Share Posted July 31, 2004 Jason. The N47 has the tin liner for the exhaust port, as does the P79. If you read the posts on this site and the Internet Z Club, you will note that there are a number pumping up the P79. In stock form, it is reportedly as good as the P90 Turbo Head. The problem is you can't modify the exhaust on these two heads. What you've got from the factory is it! The P90 has the same improved combustion chamber as the P79 with the ports of the E88 or N42. I personally went through this, I have a P79, (2) N42s and a P90. the P90 is presently being pocket ported in my spare time (no rush). I will also match the ports to my headers and intake MSA 6-3-2 header (thick flange) and 1975 non-egr fuel injected intake. Of the heads you have, I would prefer the E88 due to the ports (personal phobia against the "tin" in the exhaust ports). If it is an early E88, with the squish area below the indent, then I would have the seats opened for the 280 size valves and hardened valve seats installed. If it is the later head (260), you have larger exhaust valves, but not the hardened seats (no lead fuel) and the small intakes. The the exhaust should have new hardened seats and the intakes should have new seats or the seats cut for the larger intake valve and the larger valves installed. If you are not going to do anything to improve the head (dollars$$$$) stick with the N47, it already has the large valves, just install the flat top pistons from a late 81-83 280ZX motor for appx 9.8:1. Everything is money!! For better results use a P79, shave it .080 and shim the cam towers a like amount. Use the valves from your N47 head .080 longer (make up the difference of the shims under the cam tower. Install your flat top pistons and with a cam etc. have the potential for 170 RWHP. Hp is what the sites seem to suggest. One of the folks on this site dynoed 164 with a basically stock motor and a P90 head @.080. Good luck. ecp48 Quote Link to comment Share on other sites More sharing options...
ecp48 Posted July 31, 2004 Share Posted July 31, 2004 Jason. The N47 has the tin liner for the exhaust port, as does the P79. If you read the posts on this site and the Internet Z Club, you will note that there are a number pumping up the P79. In stock form, it is reportedly as good as the P90 Turbo Head. The problem is you can't modify the exhaust ports on these two heads. What you've got from the factory is it! The P90 has the same improved (better, increased squish, should provide less detonation) combustion chamber as the P79 with the ports of the E88 or N42. I personally went through this evaluation. I have a P79, (2) N42s and a P90. The P90 is presently being pocket ported in my spare time (no rush). I will also match the ports to my headers and intake (MSA 6-3-2 header (thick flange) and 1975 non-egr fuel injected intake) and shave the head .080 for appx 9.8:1 compression. Of the heads you have, I would personally prefer the E88 because of the ports (personal phobia against the "tin" in the exhaust ports). If it is an early E88, with the squish area below the indent, then I would have the seats opened for the 280 size valves and hardened valve seats installed. If it is the later head (73 240 or 260), you may have larger exhaust valves(260 only), but not the hardened seats (no lead fuel) and the small intakes. The exhaust should have/need new hardened seats and the intakes should have new seats or the seats cut for the larger intake valve and the larger valves installed. If you are not going to do anything to improve the head (dollars$$$$) stick with the N47, it already has the large valves, just install the flat top pistons from a late 81-83 280ZX motor for appx 9.8:1. Everything is money!! For better results use a P79, shave it .080 and shim the cam towers a like amount. Use the valves from your N47 head .080 longer (make up the difference of the shims under the cam tower. Install your flat top pistons and with a cam etc., have the potential for 170 RWHP. This HP is what the site(s) seem to suggest. One of the folks on this site dynoed 164 RWHP with a basically stock motor and a P90 head @.080 with a header. Good luck. Quote Link to comment Share on other sites More sharing options...
e_racer1999 Posted July 31, 2004 Author Share Posted July 31, 2004 thanks for the info! yeah, i am probably going to port & polish the N47 for now and get the domed pistons. i don't really want to mill the head b/c i don't want to worry about the tension in the timing chain. -jason Quote Link to comment Share on other sites More sharing options...
ecp48 Posted August 1, 2004 Share Posted August 1, 2004 Jason, Be real careful with the port and polish. You have a stainless steel liner in the exhaust port. All you can do is "rip it out" and you end up with a ragged opening in stead of a port. Do some mild work blending the bowls and clean up any rough edges in the combustion chamber and thats all! ecp48 Quote Link to comment Share on other sites More sharing options...
z-ya Posted August 2, 2004 Share Posted August 2, 2004 Since you are looking to build a streetable motor, I'd go with either the N47 or a P79. You will need to spend more money on the P79 to raise the compression ratio to where you want it (shaved, cam tower spacers). So since they are both round port, I'd select the N47. The N47 is decent head in stock form. I'm getting 164WHP through a totally stock N47. If you have a square port header, find an N42. Same combustion chamber size, but with a square port. If you are going for more than street performance, go with the P79 or P90, but be ready to spend a bit more on head work. Pete Quote Link to comment Share on other sites More sharing options...
e_racer1999 Posted August 2, 2004 Author Share Posted August 2, 2004 i'm probably going to stick with the N47 so i won't have to oversize the valves in the E88. i also want to keep the E88 in good (stock) condition in case i want to restore the car.... Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted August 3, 2004 Share Posted August 3, 2004 I've gotta chime in that there is still no credible evidence that the P-heads are superior to the N-heads, stock or modified. There's just no such evidence (to my knowledge) out there. The ONLY argument I hear lauding the P chambers is that the chambers LOOK better. Lots of stock and modded N-heads that don't suffer from the "detonation-prone" problems they're supposed to have. I for one wouldn't go to the effort of shaving and shimming a P-head when an N-head doesn't require nearly the butchery to get the desired compression ratio for an NA application. For a turbo, I'd use the P90, no question, again because of compression ratio. Quote Link to comment Share on other sites More sharing options...
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